1. Department of Chemistry, Yale University, New Haven, Connecticut 06520, U.S.A.
2. Yale Energy Sciences Institute, Yale University, West Haven, Connecticut 06516, U.S.A.
3. Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, U.S.A.
4. Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, MC 0358, La Jolla, California 92093, U.S.A.